JP2010198987A - Manufacturing method of power storage device, and power storage device - Google Patents
Manufacturing method of power storage device, and power storage device Download PDFInfo
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Classifications
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Secondary Cells (AREA)
- Electric Double-Layer Capacitors Or The Like (AREA)
- Fixed Capacitors And Capacitor Manufacturing Machines (AREA)
- Cell Separators (AREA)
Abstract
Description
本発明は、蓄電デバイスの製造方法および蓄電デバイスに関する。詳しくは、電極シートとセパレータを含む電極群を有する電池、キャパシタなどの蓄電デバイスの製造方法および当該製造方法により得られた蓄電デバイスに関するものである。 The present invention relates to a method for manufacturing an electricity storage device and an electricity storage device. Specifically, the present invention relates to a method for manufacturing a power storage device such as a battery or a capacitor having an electrode group including an electrode sheet and a separator, and a power storage device obtained by the manufacturing method.
コンデンサ、キャパシタ、電池等の蓄電デバイスは電極群を含み、一般に、電極群は、セパレータ、２種類の電極シートなどの電極群構成部材から構成され、電極群は、セパレータを介して２種類の電極シートを任意の形状に積層して、または積層・巻回して作製される。この場合、電極群におけるセパレータおよび２種類の電極シートはできるだけ密着していることが望ましく、これらが剥がれ易いと、電極群に緩みが生じ、電極群構成部材間に隙間が生じることになる。このことは、例えば、二次電池の場合には、正極負極間の距離にばらつきが生じることを意味し、これにより電池の内部抵抗が局所的に増加し、一部に充放電が集中し、充放電特性などの電池特性の加速的な劣化や、安全性低下を惹起するという懸念があった。
また、蓄電デバイス全体がその動作時に発熱した場合には、電極群構成部材間の隙間はより広がるという傾向にあり、この傾向は巻回して作製される巻回型電極群を使用した蓄電デバイスに於いて特に顕著であった。
An electricity storage device such as a capacitor, a capacitor, or a battery includes an electrode group. In general, the electrode group includes electrode group constituent members such as a separator and two types of electrode sheets, and the electrode group includes two types of electrodes via the separator. It is produced by laminating sheets in an arbitrary shape, or laminating and winding. In this case, it is desirable that the separator and the two types of electrode sheets in the electrode group are as close as possible. If they are easily peeled off, the electrode group is loosened and a gap is formed between the electrode group constituent members. This means that, for example, in the case of a secondary battery, the distance between the positive electrode and the negative electrode varies, thereby increasing the internal resistance of the battery locally, and charge / discharge is concentrated in part. There was a concern that battery characteristics such as charge / discharge characteristics may be accelerated and safety may be lowered.
In addition, when the entire power storage device generates heat during its operation, the gap between the electrode group constituent members tends to widen, and this tendency is applied to a power storage device using a wound electrode group produced by winding. In particular.
電極群構成部材同士をより密着させる手段としては、例えば、特許文献１では、円柱状又は楕円形状に巻回した電極群を、押し潰して扁平状に形成して電極群構成部材同士を密着させた後に、円筒型、角型の外装内に挿入する方法が採られている。
また、例えば、外装材に金属ラミネート樹脂フィルムを使用したフィルムケース型の蓄電デバイスでは、ケース内部を減圧して大気圧によりケース外部から内部を加圧することにより、電極群を圧縮して、電極群構成部材同士を密着させる方法が採られている。
As a means for bringing the electrode group constituent members into closer contact, for example, in Patent Document 1, the electrode group wound in a columnar shape or an elliptical shape is crushed and formed into a flat shape to bring the electrode group constituent members into close contact with each other. After that, a method of inserting into a cylindrical or square exterior is adopted.
Further, for example, in a film case type electricity storage device using a metal laminate resin film as an exterior material, the inside of the case is depressurized and the inside of the case is pressurized from the outside of the case by atmospheric pressure, thereby compressing the electrode group, A method is used in which the constituent members are brought into close contact with each other.
しかしながら、上記の従来方法による蓄電デバイスにおいては、動作時に、外装内部のガス発生や電極群の膨張収縮などにより、外装の変形や電極群構成部材の剥がれがおこり、電極群構成部材間の隙間の増加、電極群の変形が生じ、その結果、蓄電デバイスの内部抵抗が増加して、蓄電デバイスの性能の劣化、安全性の低下を招く虞があり、上記の懸念を解消する点で未だ十分とは言い難い。また、巻回型電極群を使用した蓄電デバイスの場合には、巻回の際に発生した電極群内部の張力がかかった状態になっていることから、電極群構成部材間の隙間が大きくなりやすく、特に問題となる。
かかる状況下、本発明は、蓄電デバイス動作時の電極群構成部材間の隙間の増加、電極群の変形をできるだけ抑制し、これに伴う蓄電デバイスの内部抵抗の増加をできるだけ抑制することにより、蓄電デバイスの性能の劣化、安全性の低下をより防ぐことができる蓄電デバイス、および蓄電デバイスの製造方法を提供することを目的とする。
However, in the electricity storage device according to the conventional method described above, during operation, due to gas generation inside the exterior or expansion / contraction of the electrode group, deformation of the exterior or peeling of the electrode group constituent member occurs, and a gap between the electrode group constituent members is not generated. As a result, the internal resistance of the electricity storage device increases, resulting in deterioration of the performance of the electricity storage device and a decrease in safety, which is still sufficient to eliminate the above-mentioned concerns. Is hard to say. In addition, in the case of an electricity storage device using a wound electrode group, since the tension inside the electrode group generated during winding is in a state of being applied, the gap between the electrode group constituent members becomes large. Easy and especially problematic.
Under such circumstances, the present invention suppresses an increase in the gap between the electrode group constituent members during the operation of the power storage device and the deformation of the electrode group as much as possible, and suppresses an increase in the internal resistance of the power storage device associated therewith as much as possible. It is an object of the present invention to provide an electricity storage device that can further prevent deterioration in device performance and safety, and a method for manufacturing the electricity storage device.
本発明者は、以下の構成を採用することにより、本発明の課題を解決することが可能であることを見出し、本発明を完成するに至った。 The present inventor has found that the problems of the present invention can be solved by adopting the following configuration, and has completed the present invention.
すなわち、本発明は、第１の電極シートと第２の電極シートとセパレータとを、積層して、または積層・巻回して得られる電極群を加熱下に加圧する工程を含む蓄電デバイスの製造方法に係るものである。なお、得られる電極群において、第１の電極シートと第２の電極シートは、セパレータによって隔離されている。 That is, the present invention relates to a method for producing an electricity storage device including a step of pressurizing under heating an electrode group obtained by laminating or laminating and winding a first electrode sheet, a second electrode sheet, and a separator. It is related to. In the obtained electrode group, the first electrode sheet and the second electrode sheet are separated by a separator.
本発明の蓄電デバイスの製造方法の特徴は、電極群を加熱下に加圧することにある。
電極群を加熱することによって電極群構成部材である、第１の電極シートと、第２の電極シートおよびセパレータの柔軟性が向上し、加圧することによって、各電極群構成部材の密着性が向上する。
A feature of the method for manufacturing an electricity storage device of the present invention is that the electrode group is pressurized under heating.
The flexibility of the first electrode sheet, the second electrode sheet, and the separator, which are electrode group constituent members, is improved by heating the electrode group, and the adhesion of each electrode group constituent member is improved by applying pressure. To do.
なお、電極群が、第１の電極シートと第２の電極シートとセパレータとを、積層・巻回して得られる巻回型電極群である場合、加熱下に加圧する工程において、該電極群における巻回軸に垂直な断面を扁平状に形成することが好ましい。
上述のように巻回型電極群は、巻回による内部張力の低下によって、電極群構成部材が広がりやすい傾向があるが、加熱した状態で扁平状になるまで各電極群構成部材を密着させることによって、成形後の電極群の変形を抑制することができる。
When the electrode group is a wound electrode group obtained by laminating and winding the first electrode sheet, the second electrode sheet, and the separator, in the step of applying pressure under heating, It is preferable to form a cross section perpendicular to the winding axis in a flat shape.
As described above, in the wound electrode group, the electrode group constituent members tend to spread due to a decrease in internal tension due to winding, but the electrode group constituent members are brought into close contact with each other until they become flat when heated. Thus, deformation of the electrode group after molding can be suppressed.
また、第１の電極シート、第２の電極シートおよびセパレータの少なくとも一つの電極群構成部材が熱可塑性であり、かつ、加熱下に加圧する工程における加熱温度が、前記熱可塑性を有する電極群構成部材の可塑化温度以上、溶融温度もしくは分解温度以下であることが望ましい。
可塑化温度以上で加熱することによって、熱可塑性を有する電極群構成部材が軟化するため形状が変化しやすくなり、さらに加熱後に硬化することでその形状が保持されるため、各電極群構成部材が密着した構造をより保つことができる。
ここで、熱可塑性を有する電極群構成部材が、セパレータ（特に積層セパレータ）である場合には特に効果的である。
なお、上記加熱温度を、溶融温度もしくは分解温度以下とすることで電極群構成部材が変質することを防止することにより、蓄電デバイスにおける各種シートの抵抗の増大により性能が低下することが回避される。
Further, at least one electrode group constituting member of the first electrode sheet, the second electrode sheet and the separator is thermoplastic, and the heating temperature in the step of applying pressure under heating is the electrode group constitution having the thermoplasticity. It is desirable that the temperature is not less than the plasticizing temperature of the member and not more than the melting temperature or decomposition temperature.
By heating at a temperature equal to or higher than the plasticizing temperature, the electrode group constituting member having thermoplasticity is softened, so that the shape is easily changed, and further, the shape is maintained by being cured after heating. A tighter structure can be maintained.
Here, it is particularly effective when the electrode group constituting member having thermoplasticity is a separator (particularly a laminated separator).
In addition, by preventing the electrode group constituent member from being altered by setting the heating temperature to be equal to or lower than the melting temperature or the decomposition temperature, it is possible to avoid deterioration in performance due to an increase in resistance of various sheets in the electricity storage device. .
本発明の製造方法は、第１の電極シートが正極であり、第２の電極シートが負極であり、非水系電解液を含有してなる蓄電デバイスの製造方法として好適であり、特に前記非水系電解液がリチウムイオンを含む蓄電デバイス（特に電池、とりわけ二次電池）である場合に好適である。 The production method of the present invention is suitable as a production method of an electricity storage device in which the first electrode sheet is a positive electrode, the second electrode sheet is a negative electrode, and contains a non-aqueous electrolyte solution. It is suitable when the electrolytic solution is an electricity storage device (particularly a battery, particularly a secondary battery) containing lithium ions.
本発明によれば、動作時の外装内部でのガス発生などによって、外装材に膨れが生じても、電極群構成部材間の隙間の増加、電極群の変形が抑制され、蓄電デバイスの内部抵抗の増加を抑制することができるため、性能の劣化、安全性の低下がより小さい蓄電デバイスを製造、提供することが出来る。 According to the present invention, even if the exterior material swells due to gas generation inside the exterior during operation, the increase in the gap between the electrode group constituent members and the deformation of the electrode group are suppressed, and the internal resistance of the electricity storage device Therefore, it is possible to manufacture and provide an electricity storage device with less performance deterioration and less safety reduction.
以下に、本発明の好適な実施形態を、図面を参照しながら説明する。
なお、本発明の実施形態の蓄電デバイスの製造方法として、気密性の金属ラミネート樹脂フィルムケースを外装としたフィルムケース型リチウムイオン二次電池の製造方法を例示するが、本発明は該形態に限ることなく、角型を含むあらゆる形状の缶を外装にした二次電池や、その他の電池の製造方法に適用できる。また、コンデンサ、キャパシタなど電池以外の蓄電デバイスの製造方法として使用することができる。
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
In addition, as a method for manufacturing an electricity storage device according to an embodiment of the present invention, a method for manufacturing a film case type lithium ion secondary battery having an airtight metal laminate resin film case as an exterior is illustrated, but the present invention is limited to this mode. Without limitation, the present invention can be applied to a secondary battery having a can of any shape including a square shape as an exterior, and other battery manufacturing methods. Further, it can be used as a method for producing an electricity storage device other than a battery, such as a capacitor and a capacitor.
図１は、本発明の実施形態に係るリチウムイオン二次電池における電極群の斜視図である。
図中、電極群６は、それぞれ細長片である電極タブ５ａが付着された第１の電極シート１、電極タブ５ｂが付着された第２の電極シート２、ならびにセパレータ３およびセパレータ４からなり、セパレータ３、第２のシート２、セパレータ４、第１のシート１の順に積層されて、巻回の軸と垂直方向に切断したときの断面が、円状または楕円形状に巻回することによって形成された電極群である。なお、巻き終わった電極群６はテープなどで固定され、フィルムケースなどの容器内に収納し、電解質を含有する有機溶媒からなる電解液を電極群に含浸させてリチウムイオン二次電池として使用される。
FIG. 1 is a perspective view of an electrode group in a lithium ion secondary battery according to an embodiment of the present invention.
In the figure, the electrode group 6 is composed of a first electrode sheet 1 to which electrode tabs 5a that are elongated pieces are attached, a second electrode sheet 2 to which electrode tabs 5b are attached, and a separator 3 and a separator 4, respectively. The separator 3, the second sheet 2, the separator 4, and the first sheet 1 are laminated in this order, and the cross section when cut in the direction perpendicular to the winding axis is formed by winding in a circular or elliptical shape. Electrode group. The wound electrode group 6 is fixed with a tape or the like, stored in a container such as a film case, and the electrode group is impregnated with an electrolyte solution containing an organic solvent and used as a lithium ion secondary battery. The
第１の電極シート１は、正極活物質としてＬｉを含む酸化物を含む正極合剤をＡｌ箔に塗布して作製された導電性シートであり、正極としての機能を有する。この正極シート（第１の電極シート１）は、通常、正極集電体と、正極集電体の上に担持された正極合剤とから構成され、正極シート（第１の電極シート１）の厚みは、通常、５〜５００μｍ程度である。
正極集電体として、本実施形態では、Ａｌが使用されているが、薄膜に加工しやすいものであればよく、Ａｌ以外にもＮｉ、ステンレスなどの金属などを用いることができる。正極集電体の形状としては、例えば、箔状、平板状、メッシュ状、ネット状、ラス状、パンチングメタル状若しくはエンボス状であるものまたはこれらを組み合わせたもの（例えば、メッシュ状平板など）等が挙げられる。
The first electrode sheet 1 is a conductive sheet produced by applying a positive electrode mixture containing an oxide containing Li as a positive electrode active material to an Al foil, and has a function as a positive electrode. This positive electrode sheet (first electrode sheet 1) is usually composed of a positive electrode current collector and a positive electrode mixture supported on the positive electrode current collector, and the positive electrode sheet (first electrode sheet 1) The thickness is usually about 5 to 500 μm.
In this embodiment, Al is used as the positive electrode current collector. However, any material that can be easily processed into a thin film may be used, and metals such as Ni and stainless steel can be used in addition to Al. Examples of the shape of the positive electrode current collector include a foil shape, a flat plate shape, a mesh shape, a net shape, a lath shape, a punching metal shape, an embossed shape, or a combination thereof (for example, a mesh flat plate). Is mentioned.
正極合剤は、正極活物質及び必要に応じて導電材やバインダーを含み、それぞれが従来公知の材料から作製することができる。
正極活物質としてのＬｉを含む酸化物としては、例えば、ＬｉＣｏＯ2、ＬｉＮｉＯ2、Ｌｉ（Ｎｉ,Ｃｏ）Ｏ2、Ｌｉ（Ｎｉ,Ｍｎ）Ｏ2、Ｌｉ（Ｎｉ,Ｍｎ,Ｃｏ）Ｏ2、ＬｉＭｎ2Ｏ4、Ｌｉ（Ｍｎ,Ｆｅ）2Ｏ4、ＬｉＦｅＰＯ4、ＬｉＭｎＰＯ4などを挙げることができ、これらは１種あるいは２種以上を混合して使用することができる。
前記導電材としては炭素材料を用いることができ、炭素材料として黒鉛粉末、カーボンブラック、カーボンナノチューブなどの繊維状炭素材料などを挙げることができる。
前記バインダーとしては、熱可塑性樹脂を用いることができ、例えば、ポリフッ化ビニリデン（以下、ＰＶＤＦということがある。）、ポリテトラフルオロエチレン（以下、ＰＴＦＥということがある。）などのフッ素樹脂、ポリエチレン、ポリプロピレンなどのポリオレフィン樹脂等が挙げられる。また、これらの２種以上を混合して用いてもよい。
The positive electrode mixture includes a positive electrode active material and, if necessary, a conductive material and a binder, and each can be made from a conventionally known material.
Examples of the oxide containing Li as the positive electrode active material include LiCoO 2 , LiNiO 2 , Li (Ni, Co) O 2 , Li (Ni, Mn) O 2 , Li (Ni, Mn, Co) O 2 , LiMn 2 O 4 , Li (Mn, Fe) 2 O 4 , LiFePO 4 , LiMnPO 4 and the like can be mentioned, and these can be used alone or in combination of two or more.
A carbon material can be used as the conductive material, and examples of the carbon material include fibrous carbon materials such as graphite powder, carbon black, and carbon nanotubes.
As the binder, a thermoplastic resin can be used. For example, a fluororesin such as polyvinylidene fluoride (hereinafter sometimes referred to as PVDF) or polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), polyethylene, and the like. And polyolefin resins such as polypropylene. Moreover, you may use these 2 types or more in mixture.
正極集電体に正極合剤を担持させる方法としては、加圧成形する方法、または有機溶媒などを用いてペースト化し、正極集電体上に塗布、乾燥後プレスするなどして固着する方法が挙げられる。正極合剤を正極集電体へ塗布する方法としては、例えば、スリットダイ塗工法、スクリーン塗工法、バー塗工法等が挙げられる。 As a method of supporting the positive electrode mixture on the positive electrode current collector, there is a method of pressure forming, or a method of pasting using an organic solvent or the like, applying onto the positive electrode current collector, drying and pressing to fix the positive electrode current collector. Can be mentioned. Examples of the method for applying the positive electrode mixture to the positive electrode current collector include a slit die coating method, a screen coating method, and a bar coating method.
本実施形態において、第２の電極シート２は、グラファイト（黒鉛粉末）をＣｕ箔に塗布して作製された導電性シートであり、負極としての機能を有する。
この負極シート（第２の電極シート２）は、通常、炭素材料などの負極材料、必要に応じてバインダーや導電材を含む負極合剤を負極集電体に担持させて製造することができる。この負極シート（第２の電極シート２）の厚みは、通常、５〜５００μｍ程度である。
負極集電体として、本実施形態では、Ｃｕが使用されているが、他の導電性材料でもよく、例えば、Ｎｉ、ステンレスなどを挙げることができる。一方で、リチウムと合金を作り難い点、薄膜に加工しやすいという点で、Ｃｕが好適である。また、導電材およびバインダーとしては、上述の正極シートと同様の材料を挙げることができる。
該負極集電体に負極合剤を担持させる方法としては、上記の正極の場合と同様であり、加圧成形による方法、溶媒などを用いてペースト化し負極集電体上に塗布、乾燥後プレスし圧着する方法等が挙げられる。
In the present embodiment, the second electrode sheet 2 is a conductive sheet produced by applying graphite (graphite powder) to Cu foil, and has a function as a negative electrode.
This negative electrode sheet (second electrode sheet 2) can be usually produced by supporting a negative electrode material such as a carbon material and a negative electrode mixture containing a binder and a conductive material as required on a negative electrode current collector. The thickness of this negative electrode sheet (second electrode sheet 2) is usually about 5 to 500 μm.
In this embodiment, Cu is used as the negative electrode current collector. However, other conductive materials may be used, and examples thereof include Ni and stainless steel. On the other hand, Cu is preferable because it is difficult to make an alloy with lithium and it can be easily processed into a thin film. Moreover, as a conductive material and a binder, the same material as the above-mentioned positive electrode sheet can be mentioned.
The method for supporting the negative electrode mixture on the negative electrode current collector is the same as in the case of the positive electrode described above, and is formed into a paste using a method by pressure molding, a solvent or the like, applied onto the negative electrode current collector, dried and then pressed. And a method of pressure bonding.
なお、電流の出し入れを行うために、第１の電極シート１、第２の電極シート２に付着された電極タブ５ａ，５ｂは、本実施形態では、Ｃｕが使用されているが、十分な電子導電性を有する材料であればよく、Ｃｕ、Ｎｉ、ステンレスなどを挙げることができ、その他にも、公知の材料からなる電極タブを使用することができる。また、電極シートと電極タブ５ａ，５ｂを付着する方法も特に限定されず、通常、溶接で行われる。 In this embodiment, Cu is used for the electrode tabs 5a and 5b attached to the first electrode sheet 1 and the second electrode sheet 2 in order to input and output current. Any material having electrical conductivity may be used, and examples thereof include Cu, Ni, and stainless steel. In addition, an electrode tab made of a known material can be used. Further, the method of attaching the electrode sheet and the electrode tabs 5a and 5b is not particularly limited, and is usually performed by welding.
セパレータ３及びセパレータ４は、厚み１０〜３０μｍの多孔性ポリエチレンシートが使用され、その中には適量の電解液を注入されている。セパレータの厚みは、特に限定されないが、通常、５〜２００μｍ（好適には５〜４０μｍ）である。
セパレータ３，４は、熱可塑性樹脂であることが望ましく、本実施形態では多孔性ポリエチレンシートを使用したが、他の材料からなる多孔性シートでもよく、他の材料として、具体的には、ポリエチレン、ポリプロピレンなどのポリオレフィン樹脂、フッ素樹脂、含窒素芳香族重合体が挙げられる。
また、セパレータ３，４は、両電極シートの短絡を防止する機能および過充電時のシャットダウン機能を有するが、シャットダウン後の熱破膜抑制機能（耐熱機能）を持たせる為に、耐熱性を有する耐熱性多孔層と、ポリエチレン樹脂等の熱可塑性樹脂を含有する多孔性シートとが積層された積層セパレータを用いることもできる。
耐熱性多孔層は、耐熱樹脂からなってもよいし、無機粒子からなってもよいし、これらが混合されてなってもよい。耐熱樹脂としては、含窒素芳香族重合体を用いることが好ましく、積層セパレータとしては、含窒素芳香族重合体を有する耐熱性多孔層と、多孔性ポリエチレンシートとが積層された積層セパレータが、二次電池用セパレータとして耐熱性の面、シャットダウンの性能面で好適である。積層セパレータとしては、例えば特開２０００−３０６８６号公報、特開平１０−３２４７５８号公報等に記載の積層セパレータを挙げることができる。
As the separator 3 and the separator 4, a porous polyethylene sheet having a thickness of 10 to 30 μm is used, and an appropriate amount of electrolytic solution is injected therein. Although the thickness of a separator is not specifically limited, Usually, it is 5-200 micrometers (preferably 5-40 micrometers).
The separators 3 and 4 are desirably thermoplastic resins. In this embodiment, a porous polyethylene sheet is used. However, a porous sheet made of another material may be used. And polyolefin resins such as polypropylene, fluororesins, and nitrogen-containing aromatic polymers.
In addition, the separators 3 and 4 have a function of preventing a short circuit between both electrode sheets and a shutdown function at the time of overcharge, but have a heat resistance in order to have a function of suppressing thermal film breakage (heat resistance function) after shutdown. A laminated separator in which a heat-resistant porous layer and a porous sheet containing a thermoplastic resin such as polyethylene resin are laminated can also be used.
The heat resistant porous layer may be made of a heat resistant resin, inorganic particles, or a mixture thereof. As the heat-resistant resin, a nitrogen-containing aromatic polymer is preferably used. As the laminated separator, a laminated separator in which a heat-resistant porous layer having a nitrogen-containing aromatic polymer and a porous polyethylene sheet are laminated is used. As a secondary battery separator, it is suitable in terms of heat resistance and shutdown performance. Examples of the laminated separator include laminated separators described in JP 2000-30686 A, JP 10-324758 A, and the like.
上述のように作製された、電極群構成部材が積層、巻回された電極群６は、電極群６の形状に合わせた成形型に配置され、適当な温度および圧力の下で成形される。
本発明の製造方法においては、電極群６を成形する際に加熱下で加圧する工程を含むことに特徴の一つがある。
加圧すると同時に加熱することで、電極群６の成形性が向上し、円柱状または楕円形状に巻回された電極群６が扁平状に、より強固に形成され、各電極群構成部材の密着性が向上する。
The electrode group 6 made by laminating and winding the electrode group constituent members produced as described above is placed in a molding die that matches the shape of the electrode group 6 and molded under an appropriate temperature and pressure.
One feature of the manufacturing method of the present invention is that it includes a step of applying pressure under heating when the electrode group 6 is formed.
By heating at the same time as pressurization, the formability of the electrode group 6 is improved, and the electrode group 6 wound in a columnar shape or an elliptical shape is more firmly formed in a flat shape, and the electrode group constituent members are closely attached. Improves.
特に電極群６を構成する電極群構成部材として、熱可塑性を有するものを使用する場合には、その熱可塑性を有する電極群構成部材の可塑化温度以上溶融温度以下で、加熱を行うと、その電極群構成部材が容易に変形することができるため、内部張力の低下をほとんど発生させることなく、扁平状の電極群を形成することができる。なお、溶融点を持たず、分解する熱可塑性樹脂を電極群構成部材として使用する場合は、該電極群構成部材の可塑化温度以上分解温度以下で加熱を行えばよい。
なお、電極シートに熱可塑性を持たせる方法として、熱可塑性樹脂を電極合剤に混合する方法が挙げられるが、混合する熱可塑性樹脂の量が多い場合には、電池容量が低下するなどの問題がある。
一方、セパレータは、それ自体が熱可塑性樹脂で構成することができるため、電極群構成部材のうち、少なくともセパレータが熱可塑性樹脂であると、セパレータ材料が変形した形状を維持でき、且つ透気度など特性に変化させることのない温度、圧力で加熱加圧成形することで、長期間使用における、電池の温度変化、ガス発生等による電池の膨れが生じても、巻回した電極群が変形したり、緩みが発生したりすることなく、電池の内部抵抗の変化を低減することが出来る。
In particular, when using an electrode group constituting member constituting the electrode group 6 having a thermoplastic property, when heating is performed at a temperature equal to or higher than a plasticizing temperature of the electrode group constituting member having the thermoplastic property and below a melting temperature, Since the electrode group constituent members can be easily deformed, a flat electrode group can be formed with almost no decrease in internal tension. In addition, when using the thermoplastic resin which does not have a melting point and decomposes | disassembles as an electrode group structural member, what is necessary is just to heat above the plasticization temperature of this electrode group structural member and below a decomposition temperature.
In addition, as a method for imparting thermoplasticity to the electrode sheet, a method of mixing a thermoplastic resin with the electrode mixture can be mentioned. However, when the amount of the thermoplastic resin to be mixed is large, there is a problem such as a decrease in battery capacity. There is.
On the other hand, since the separator itself can be composed of a thermoplastic resin, if at least the separator is a thermoplastic resin among the electrode group constituent members, the shape of the separator material can be maintained and the air permeability can be maintained. By heating and pressing at a temperature and pressure that do not change the characteristics, the wound electrode group is deformed even if the battery swells due to battery temperature change or gas generation during long-term use. The change in the internal resistance of the battery can be reduced without causing any looseness.
次に、上記手法にて作製した電極群６を、本発明の加熱下に加圧成形する工程について、図２に基づき詳述する。図２は、本発明で使用可能な加圧加熱成型器の断面概略図である。
図２において、加圧加熱成型器７は、下型８ａと上型８ｂとかならなる成型器８、ならびに成型器８を加熱することができるヒーター部９からなる。
下型８ａは巻回した電極群６の形状に合わせた成形型であり、電極群６は下型８ａに収容されて、ヒーター部９によって所定の温度まで加熱された状態で、上型８ｂによって加圧され、成形される。
Next, the step of pressure-forming the electrode group 6 produced by the above method under heating according to the present invention will be described in detail with reference to FIG. FIG. 2 is a schematic cross-sectional view of a pressure heating molding machine that can be used in the present invention.
In FIG. 2, the pressurizing and heating molder 7 includes a molder 8 including a lower mold 8 a and an upper mold 8 b, and a heater unit 9 that can heat the molder 8.
The lower die 8a is a molding die that matches the shape of the wound electrode group 6. The electrode group 6 is accommodated in the lower die 8a and heated to a predetermined temperature by the heater unit 9, and is then moved by the upper die 8b. Pressurized and molded.
加熱温度は、使用する電極群構成部材の中の熱可塑性材料により適宜決定されるが、１２０℃〜１４０℃のシャットダウン温度を持つポリエチレンを含むセパレータを使用した場合加熱温度は５０℃〜８０℃が望ましい。
一方、成形圧力も使用する電極群構成部材により適宜決定され、一般には、圧力０．５ＭＰａ〜１０ＭＰａ、加圧時間３０秒〜５分である。このように、最適の圧力、温度はセパレータをはじめとした、電極群構成部材の材質、厚みによって適宜決定される。
例えば、温度、圧力が高過ぎると、１００ｃｃの空気の通過時間（透気度：秒/１００ｃｃ）の増加、電極群の絶縁不良などが生じる。このように、圧力、温度設定は、透気度の変化が少なく、電極群の絶縁が保たれ、電極群の扁平状に成形が出来ていることが必要である。
The heating temperature is appropriately determined depending on the thermoplastic material in the electrode group constituting member to be used. When a separator containing polyethylene having a shutdown temperature of 120 ° C. to 140 ° C. is used, the heating temperature is 50 ° C. to 80 ° C. desirable.
On the other hand, the forming pressure is also appropriately determined depending on the electrode group constituent member to be used, and is generally a pressure of 0.5 MPa to 10 MPa and a pressurization time of 30 seconds to 5 minutes. As described above, the optimum pressure and temperature are appropriately determined depending on the material and thickness of the electrode group constituent members including the separator.
For example, if the temperature and pressure are too high, the passage time of 100 cc air (air permeability: seconds / 100 cc) increases, insulation failure of the electrode group, and the like occur. As described above, the pressure and temperature settings need to have a small change in air permeability, maintain insulation of the electrode group, and be formed into a flat shape of the electrode group.
なお、上記で加熱加圧成形した電極群は、Ａｌラミネート樹脂フィルムからなるフィルムケースに挿入し、その後、フィルムケース内の電極群に電解液を含浸させる。含浸させた後、余分な電解液を抽出し、正極電極タブと負極タブが外部に出るように減圧しながら封止し、本発明の実施形態の蓄電デバイスの一つであるフィルムケース型電池が作製される。 In addition, the electrode group heat-press-molded above is inserted into a film case made of an Al laminate resin film, and then the electrode group in the film case is impregnated with an electrolytic solution. After impregnation, the excess electrolyte solution is extracted and sealed while reducing the pressure so that the positive electrode tab and the negative electrode tab are exposed to the outside, and a film case type battery that is one of the electricity storage devices of the embodiment of the present invention is obtained. Produced.
なお、電解液としては、従来公知の非水系電解液が使用され、非水系電解液は、通常、電解質および有機溶媒を含有する。本実施形態であるリチウムイオン二次電池の場合、電解質はリチウムイオン二次電池に一般に使用されるものであればよく、例えば、ＬｉＣｌＯ4、ＬｉＰＦ6、ＬｉＡｓＦ6、ＬｉＳｂＦ6、ＬｉＢＦ4、ＬｉＣＦ3ＳＯ3、ＬｉＮ（ＳＯ2ＣＦ3）2、ＬｉＮ（ＳＯ2Ｃ2Ｆ5）2、ＬｉＮ（ＳＯ2ＣＦ3）（ＣＯＣＦ3）、Ｌｉ（Ｃ4Ｆ9ＳＯ3）、ＬｉＣ（ＳＯ2ＣＦ3）3、Ｌｉ2Ｂ10Ｃｌ10、ＬｉＢＯＢ（ここで、ＢＯＢは、bis(oxalato)borateのことである。）、低級脂肪族カルボン酸リチウム塩、ＬｉＡｌＣｌ4などのリチウム塩が挙げられ、これらの２種以上の混合物を使用してもよい。電池の容量を高める意味では、電解質は、ＬｉＰＦ6、ＬｉＡｓＦ6、ＬｉＳｂＦ6、ＬｉＢＦ4、ＬｉＣＦ3ＳＯ3、ＬｉＮ（ＳＯ2ＣＦ3）2およびＬｉＣ（ＳＯ2ＣＦ3）3からなる群より選ばれるフッ素化合物を、少なくとも１種以上用いることが好ましい。また、有機溶媒としては、例えばプロピレンカーボネート（ＰＣ）、エチレンカーボネート（ＥＣ）、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、エチルメチルカーボネート（ＥＭＣ）、４−トリフルオロメチル−１，３−ジオキソラン−２−オン、１，２−ジ（メトキシカルボニルオキシ）エタンなどのカーボネートが挙げられ、これらは２種以上混合して用いてもよい。カーボネートの中でも、難分解性であるという観点で、エチレンカーボネート（ＥＣ）、ジメチルカーボネート（ＤＭＣ）およびエチルメチルカーボネート（ＥＭＣ）を含む混合溶媒を用いることが好ましい。 As the electrolytic solution, a conventionally known non-aqueous electrolytic solution is used, and the non-aqueous electrolytic solution usually contains an electrolyte and an organic solvent. A lithium ion secondary battery which is the present embodiment, the electrolyte may be those commonly used in lithium ion secondary batteries, for example, LiClO 4, LiPF 6, LiAsF 6, LiSbF 6, LiBF 4, LiCF 3 SO 3 , LiN (SO 2 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2 , LiN (SO 2 CF 3 ) (COCF 3 ), Li (C 4 F 9 SO 3 ), LiC (SO 2 CF 3 ) 3 , Li 2 B 10 Cl 10 , LiBOB (where BOB is bis (oxalato) borate), lithium salt such as lower aliphatic carboxylic acid lithium salt, LiAlCl 4, etc. A mixture of two or more of these may be used. In order to increase the capacity of the battery, the electrolyte is selected from the group consisting of LiPF 6 , LiAsF 6 , LiSbF 6 , LiBF 4 , LiCF 3 SO 3 , LiN (SO 2 CF 3 ) 2 and LiC (SO 2 CF 3 ) 3. It is preferable to use at least one fluorine compound. Examples of the organic solvent include propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), 4-trifluoromethyl-1,3-dioxolane. Examples include carbonates such as 2-one and 1,2-di (methoxycarbonyloxy) ethane, and these may be used as a mixture of two or more. Among the carbonates, it is preferable to use a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) from the viewpoint of being hardly decomposable.
以上、本発明の実施形態として、金属ラミネート樹脂フィルムからなるフィルムケースを外装とするリチウムイオン二次電池の製造方法について述べたが、本発明の製造方法は、該フィルムケースに限らず、角型缶、円筒型缶など、あらゆる外装の二次電池や、その他の電池ならびに電池以外にも同様な電極群を使用するするコンデンサ、キャパシタなどの蓄電デバイスに於いて適用される。
また、本発明の製造方法によって、製造された電極群を用いてなる蓄電デバイスは、長期間使用にも耐えることができる。
As mentioned above, as the embodiment of the present invention, the manufacturing method of the lithium ion secondary battery having the film case made of the metal laminated resin film as the exterior has been described. However, the manufacturing method of the present invention is not limited to the film case, and is rectangular. The present invention can be applied to secondary batteries with various exteriors such as cans and cylindrical cans, other batteries, and power storage devices such as capacitors and capacitors that use similar electrode groups in addition to batteries.
Moreover, the electrical storage device using the electrode group manufactured by the manufacturing method of the present invention can withstand long-term use.
次に、本発明を実施例によりさらに詳細に説明する。 Next, the present invention will be described in more detail with reference to examples.
上記実施形態に係るリチウムイオン二次電池を作製した。各電極群構成部材は以下のとおりである。
第１の電極シート（正極シート）
正極集電体：Ａｌ箔 （幅：４．４ｃｍ、長さ：４７ｃｍ）
正極合剤
・正極活物質：ＬｉＣｏＯ2（９２重量％）
・導電材：アセチレンブラック（３重量％）
・バインダー：ポリフッ化ビニリデン＋カルボキシメチルセルロース（５重量％）
第２の電極シート（負極シート）
負極集電体：Ｃｕ箔 （幅：４．６ｃｍ、長さ：５７ｃｍ）
負極合剤
・負極活物質：グラファイト（９８重量％）
・バインダー：カルボキシメチルセルロース（２重量％）
セパレータ
・耐熱性多孔層（アラミドおよびアルミナ）と多孔性ポリエチレンシートとが積層された積層セパレータ（幅：４．８ｃｍ、長さ：８４ｃｍ、厚み：１７μｍ）
A lithium ion secondary battery according to the above embodiment was produced. Each electrode group constituent member is as follows.
First electrode sheet (positive electrode sheet)
Positive electrode current collector: Al foil (width: 4.4 cm, length: 47 cm)
Positive electrode mixture ・ Positive electrode active material: LiCoO 2 (92 wt%)
-Conductive material: Acetylene black (3 wt%)
・ Binder: Polyvinylidene fluoride + carboxymethylcellulose (5% by weight)
Second electrode sheet (negative electrode sheet)
Negative electrode current collector: Cu foil (width: 4.6 cm, length: 57 cm)
Negative electrode mixture ・ Negative electrode active material: Graphite (98 wt%)
・ Binder: Carboxymethylcellulose (2% by weight)
Separator ・ Laminated separator in which a heat-resistant porous layer (aramid and alumina) and a porous polyethylene sheet are laminated (width: 4.8 cm, length: 84 cm, thickness: 17 μm)
上記電極群構成部材を、セパレータ、第２の電極シート、セパレータ、第１の電極シートの順に積層し、巻き取り機を使用して巻回することによって、図１で示すような巻回の軸と垂直方向に切断したときの断面が楕円状の電極群を得た。なお、電極群の作製は、露点を−３０度以下に制御した乾燥雰囲気下で行った。 The electrode group constituting member is laminated in the order of a separator, a second electrode sheet, a separator, and a first electrode sheet, and wound using a winder, whereby a winding shaft as shown in FIG. An electrode group having an elliptical cross section when cut in the vertical direction was obtained. The electrode group was produced in a dry atmosphere in which the dew point was controlled to -30 degrees or less.
［実施例１］
（１）リチウムイオン二次電池の作製
上記手法で作製した電極群を、加圧加熱成型器（テスター産業社製）に収容し、６０℃まで加熱した後に、２ＭＰａの圧力で１〜２分間保持することで、断面が扁平状の電極群を形成した。この電池群を、５０×５０×０．５ｍｍのＡｌラミネート樹脂フィルムからなる容器に収容し、電解液（１Ｍ ＬｉＰＦ6／混合溶媒（ＥＣとＤＭＣとＥＭＣとが体積比１５：１０：７５で混合された溶媒））を注液することで、実施例１のリチウムイオン二次電池を得た。作製した実施例１のリチウムイオン二次電池のＸ線ＣＴによる断面像を図３に示す。
[Example 1]
(1) Production of Lithium Ion Secondary Battery The electrode group produced by the above method is accommodated in a pressure heating molding machine (manufactured by Tester Sangyo Co., Ltd.), heated to 60 ° C., and held at a pressure of 2 MPa for 1 to 2 minutes. Thus, an electrode group having a flat cross section was formed. This battery group is contained in a container made of an Al laminate resin film of 50 × 50 × 0.5 mm, and an electrolyte (1M LiPF 6 / mixed solvent (EC, DMC, and EMC are mixed at a volume ratio of 15:10:75). The lithium ion secondary battery of Example 1 was obtained by injecting the prepared solvent)). FIG. 3 shows a cross-sectional image of the produced lithium ion secondary battery of Example 1 by X-ray CT.
（２）評価
以下の条件で、下記条件でサイクル充放電テストを繰り返した後に作製されたリチウムイオン二次電池１のＸ線ＣＴによる断面像を図４に示す。
「充放電テスト条件」
電圧範囲：３−４．２Ｖ
充電レート：２Ｃレート（１０時間で完全充電する速度）
放電レート：１Ｃレート（１０時間で完全放電する速度）
サイクル回数：２０回
(2) Evaluation FIG. 4 shows a cross-sectional image by X-ray CT of the lithium ion secondary battery 1 produced after repeating the cycle charge / discharge test under the following conditions under the following conditions.
"Charge / discharge test conditions"
Voltage range: 3-4.2V
Charging rate: 2C rate (speed to fully charge in 10 hours)
Discharge rate: 1C rate (speed of complete discharge in 10 hours)
Number of cycles: 20 times
サイクル充放電テストテスト前後の図３、図４を比較すると、充放電テスト後においてもリチウムイオン二次電池１の電極群は、フィルムケースが膨張しているにもかかわらず、電極群の断面形状は扁平状を維持していることがわかる。
なお、サイクル初回とサイクル２０回後の電池の内部抵抗は、それぞれ４０ｍΩ、５０ｍΩであった。
Comparing FIG. 3 and FIG. 4 before and after the cycle charge / discharge test, the electrode group of the lithium ion secondary battery 1 after the charge / discharge test is the sectional shape of the electrode group even though the film case is expanded. It can be seen that the flat shape is maintained.
The internal resistance of the battery after the first cycle and after 20 cycles was 40 mΩ and 50 mΩ, respectively.
［比較例１］
（１）リチウムイオン二次電池の作製
電極群を成形する際に、６０℃で加熱を行わなかった以外は、実施例と同様にして、比較例１のリチウムイオン二次電池２を得た。
[Comparative Example 1]
(1) Production of Lithium Ion Secondary Battery A lithium ion secondary battery 2 of Comparative Example 1 was obtained in the same manner as in Example except that heating was not performed at 60 ° C. when the electrode group was formed.
（２）評価
上記条件で、作製したリチウムイオン二次電池２について、充放電テスト後のＸ線ＣＴによる断面像を図５に示す。
充放電テスト前では、リチウムイオン二次電池２内部の電極群は、断面が扁平状であったが（図示せず）、充放電テスト後は、明らかに電極群が膨張し、電極群全体に緩みが生じ形状を維持できていないことがわかる。
なお、サイクル初回とサイクル２０回後の電池の内部抵抗は、それぞれ４０ｍΩ、１２０ｍΩであった。
(2) Evaluation FIG. 5 shows a cross-sectional image by X-ray CT after the charge / discharge test for the lithium ion secondary battery 2 manufactured under the above conditions.
Before the charge / discharge test, the electrode group inside the lithium ion secondary battery 2 had a flat cross section (not shown). However, after the charge / discharge test, the electrode group clearly expanded, It can be seen that loosening occurs and the shape cannot be maintained.
The internal resistance of the battery after the first cycle and after 20 cycles was 40 mΩ and 120 mΩ, respectively.
本発明の製造方法によると、動作時の電極群構成部材間の隙間の増加、電極群の変形をできるだけ抑制することができ、これに伴う内部抵抗の変化を抑制することができるため、性能の劣化、安全性の低下をより防ぐことが可能な蓄電デバイスを製造することができる。また、この蓄電デバイスは長期間使用にも耐えることができるため、本発明は工業的に極めて有望である。 According to the manufacturing method of the present invention, an increase in the gap between the electrode group constituent members during operation and the deformation of the electrode group can be suppressed as much as possible, and a change in internal resistance accompanying this can be suppressed. It is possible to manufacture an electricity storage device that can further prevent deterioration and reduction in safety. In addition, since the electricity storage device can withstand long-term use, the present invention is extremely promising industrially.
１ 第１の電極シート（正極シート）
２ 第２の電極シート（負極シート）
３，４ セパレータ
５ａ，５ｂ 電極タブ
６ 電極群
７ 加熱加圧成型器
８ 成型器
８ａ 下型
８ｂ 上型
９ ヒーター部
1 First electrode sheet (positive electrode sheet)
2 Second electrode sheet (negative electrode sheet)
3, 4 Separator 5a, 5b Electrode tab 6 Electrode group 7 Heating and pressing molding machine 8 Molding machine 8a Lower mold 8b Upper mold 9 Heater part
Claims (10)
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